Motor fuel compositions



Jersey No Drawing. Filed Dec. 15, 1958, Ser. No. 780,189

I 2 Claims. on. 44-69) This invention relates to leaded motor fuels foruse in spark-ignition internal combustion engines. The novel fuel compositions of the invention contain, in addition to an organo-lead anti-knock agent, another additive material which is an unexpected adjuvant to the organo-lead additive in suppressing knock and/or preignition in the engine during combustion of the fuel.

The additive material used with the organo-lead antiknock agent in preparing the fuel compositions of the invention consists of one or more selected reaction products of the type formed by reacting molybdenum hexacarbonyl with an alkyl-substituted benzene hydrocarbon. The products of such a reaction are stable co-ordination compounds, or complexes, of the aromatic compound with molybdenum tricarbonyl. They can be illustrated by the constitutional formula, A-Mo-(CO) in which A rep resents an alkyl-substituted benzene molecule. When incorporated in hydrocarbon motor fuels which do not contain an organo-lead anti-knock compound, these complexes do not influence the knocking tendency of the fuel in any way, i.e., in such fuels they exhibit neither antiknock nor pro-knock properties. However, it has now been discovered that a limited number of such complexes possesses the unexpected and highly desirable ability of providing a substantial synergistic octane improvement when one or more of them is used together with an organo-lead anti-knock compound as an additive combination in motor fuels. This unexpected property is unique in the specific aromatic-molybdenum tricarbonyl complexes employed as additives in accordance with this invention, and it is not possessed to any degree by other closely-related complexes of the same type. Furthermore, this behavior is all the more surprising in view of the observedfact that similar and closely-related complexes which are'outside the scope of the invention are actually antagonistic, or detrimental, to the knock-suppressing capability of the organo-lead compounds when both are present in the fuel.

In view of the above, it is an object of this invention to provide novel motor fuel compositions including a two-component additive combination which furnishes an unexpected synergistic octane improvement.

The aromatic-molybdenum tricarbonyl complexes which can be used in practicing this invention are those in which the aromatic portion consists of a hexa-substituted benzene molecule having the following generic formula:

X CH3 X CH3 portions include: hexamethylbenzene; ethylpentamethylbenzene; n-propylpentamethylbenzene; n-butylpentameth yl-dodecylpentamethylbenzene; 1-n-undecyl-3,5-dichloroin, mutual solvents and/or dispersants can conveniently 2,4,6 trimethylbenzene; 1-n-hexyl-3-bromo-2,4,5,6-tetramethylbenzene; l-n-tridecyl-2,5-di-iodo-3,4,6 trimethyl- Patented Sept. 26, 1 961 i-propylpentamethylbenzene;

benzene; l n-tetradecyl 2,6-dichloro-3,4,5-trimethylbenzene; 1 n-tetradecyl-Z-bromo-6-chloro-3,4,5 trimethyl-.. benzene and the like. While the aromatic portion of the complexes employed in accordance with the invention can vary within the above-described limits, the remaining portion consists of molybdenum co-ordinated with three carbonyl groups. Thus the entire complex consists of molybdenum co-ordinated with a selected aromatic molecule and three carbonyl groups. Mixtures of such complexes can also be used. In practicing the invention, the

use of hexamethylbenzene molybdenum tricarbonyl is distinctly preferred. 7

The aromatic molybdenum tricarbonyl complexes,

which constitute one component of the additive combina tion of the invention, areconveniently prepared. 'For example, one method comprises heating equimolar quantities of the aromatic compound and solid molybdenunr' I hexacarbonyl in the presence of an inert liquid reaction medium which is preferably a saturated hydrocarbon for a mixture of such hydrocarbons. Suitable reaction temperatures are in the range of from about 275 F. to a maximum of about 295 F. The latter temperature limi tation is significant in that molybdenum hexacarbonyl. de

composes at a temperature slightly above the upper limit ably carried out under an inert atmosphere.

It is also convenient to maintain atmospheric pressure during the. course of the reaction so that the gaseous carbon mon--. oxide, which is concurrently produced, can readily escape. The product of the reaction is essentially the solid aromatic-molybdenum tricarbonyl complex, which can be separated from the liquid medium by any convenient means such as filtration, or distillation if the boiling point of the liquid medium is below the decomposition tempera ture of the product complex. The complex is suificiently pure, as separated, for use in accordance with the invention, but it can be further purified of unreacted solid ma-' terials by extraction with a low-boiling aromatic or naph thenic solvent, such as benzene or methylcyclopentane,

followed by distillation and/ or crystallization of the pure product complex from the extract solution.

.In carrying out the invention, the aromatic-molybdenum tricarbonyl complex is incorporated in a leaded base gasoline in a minor amount which is sufiicient to improve the octane quality of the leaded base gasolinev to a significant degree. Normally, amounts of the additive in the range of from about 0.05 percent to about 2.0 percent by weight, and preferably from about 0.10

percent to about 1.0 percent, of the resulting fuel compo-' sition give good results. On occasion, however, amounts outside of the above-recited ranges can also be employed. In general, the aromatic-molybdenum tricarbonyl complexes are sufliciently soluble in gasoline hydrocarbons,

within the range of concentrations contemplated by the invention, so as to permit their homogeneous incorporation in such fuels without the use of mutual solvents and/0r dispersants. However, where the desired concentration of the aromatic-molybdenum tricarbonyl com plex in gasoline hydrocarbons exceeds its solubility therebe employed. Low-boiling, normally-liquid, substituted and unsubstituted, nononuclear aromatic compounds, or mixtures of such compounds, are suitable for use as mutual solvents or dispersants. Examples of such compounds include benzene, toluene, the xylenes, mesitylene, ethylbenzene, cumene, tert-butylbenzene and the like.

The novel spark ignition engine fuel compositions of this invention comprise mainly gasoline, i.e., fractions of petroleum hydrocarbons boiling (at atmospheric pressure) in the gasoline boiling range of from about 80 F. to about 440 F., and usually from about 90 F. to about 400 F. Both automotive gasoline and aviation gasoline are within the scope of this invention. Aviation gasoline has a more closely specified atmospheric boiling range, generally extending from a minimum of about 100 F. to a maximum of about 350 F.

Fractions of petroleum hydrocarbons boiling within the gasoline range generally contain hydrocarbons of various types such as, for example, saturated hydrocarbons (including straightand branched-chain aliphatic, and cyclic), olefins and aromatics. While blends of these hydrocarbon types in any and all proportions are suitable for use in accordance with the present invention, the results achieved tend to be more beneficial the greater the proportion of saturated hydrocarbons, and the lower the proportion of aromatics and olefins in the base fuel blend. For example, gasolines containing not less than about 50 volume percent of saturated hydrocarbons and not more than about 50 volume percent total of olefins and aromatics, are preferred for the practice of this invention. However, gasolines containing lesser proportions of saturated hydrocarbons can also be employed, and give good results.

The novel fuel compositions of the invention must also contain an organo-lead anti-knock compound. Tetraethyl lead (T.E.L.) is the most commonly used organolead anti-knock compound, and is preferred in the practice of the invention. However, other organo-lead antiknock compounds such as, for example, tetramethyl lead, tetraphenyl lead, tetraisopropyl lead, triethylmethyl lead, diethyl dimethyl lead and tetraamyl lead, also give good results. Mixtures of these compounds can also be used in practicing the invention. In automotive fuels, the organo-lead anti-knock compounds are used in amounts ranging from about 0.05 to 3.0 cc. per gallon of fuel, while in aviation fuels, a greater amount can be used, viz., up to about 6.0 cc. per gallon.

Along with the organo-lead anti-knock compound, various volatile halohydrocarbons are normally incorporated in the fuel in lead scavenging amounts, i.e., in amounts theoretically calculated to convert the lead in the organo-lead compound to volatile compounds such as the lead dihalides. Examples of halohydrocarbon lead scavengers include: organo-bromides and -chlorides such as ethylene dibromide, ethylene dichloride, and hexachloropropylene; monoand poly-halopropanes, -butanes and -pentanes; polyhaloalkyl benzenes; and mixtures thereof with each other and the like. It is to be understood that this invention contemplates the use, together with the organo-lead anti-knock compound, of all such lead scavengers as are commonly employed, and in such amounts as may be required.

The fuel compositions of the invention can contain, in addition to the novel additive combination disclosed herein, other fuel additives commonly employed in the art which are compatible with the aromatic-molybdenum tricarbonyl complex. Commonly-used fuel additives include anti-icing agents, detergents, corrosion inhibitors, color stabilizers, anti-oxidants, gum inhibitors, dyes and the like. Stabilizing additives of the amino-phenol type are not compatible with the complex, and therefore should not be used. Other anti-knock agents, such as cyclomatic manganese tricarbonyl compounds (e.g., methylcyclopentadienyl manganese tricarbonyl), bis-cyclopentadienyl iron and the iron carbonyls, can be used together with the novel additive combination disclosed herein. It is essential to the practice of this invention, only that the synergistic anti-knock additive combination, viz., an organo-lead anti-knock compound and a selected aromaticmolybdenum tricarbonyl complex, be present in suitable amounts in the motor fuel. However, it is also to be understood that this invention contemplates the use of other additives, such as scavengers, which are made necessary or desirable by the presence of the aromatic-molybdenum tricarbonyl complex in the fuel.

The following examples are presented to illustrate the significant and unexpected benefits to be derived from the practice of the invention. In all cases, the aromaticmolybdenum tricarbonyl complex was prepared from the aromatic compound and molybdenum hexacarbonyl by the method described herein.

Example I A mixture of predominantly saturated hydrocarbons boiling within the gasoline range, and having a research octane number (R.O.N.) of 81.7 as obtained by A.S.T.M. method D-908, is the base fuel in this experiment. When 0.26 weight percent of hexamethylbenzene molybdenum tricarbonyl is incorporated in this base fuel, the R.O.N. of the resultant composition remains approximately the same, viz., 81.5. This demonstrates that hexamethylbenzene molybdenum tricarbonyl, by itself, exhibits no knock-inhibiting effect when present alone in the base fuel. On the other hand, incorporation of 3 cc. of T.E.L. compound per gallon in the same base fuel, together with the customary accompanying amount of halohydrocarbon lead scavengers, raises the R.O.N. by a substantial amount, viz., from 81.7 to 94.6, as would be expected. However, addition of both hexamethyl-benzene molybdenum tricarbonyl and T.E.L. to the base fuel in the above respective concentrations unexpectedly results in raising the R.O.N. of the resultant composition to 96.5, representing a synergistic benefit of almost 2 research octane numbers. This latter composition illustrates the novel fuels of the invention.

Example II In this example, the base fuel is the unleaded base stock for a commercially available gasoline. This base fuel has a R.O.N. of 96.0, and an approximate volumetric composition of 52 percent saturated hydrocarbons and 48 percent aromatic and olefinic hydrocarbons. Addition of 3 cc. of T.E.L. per gallon to the base fuel raises the R.O.N. to 105.4. However, when 0.40 weight percent of hexaethylbenzene molybdenum tricarbonyl and 3 cc. of T.E.L. per gallon are both added to the base fuel, the R.O.N. of the resultant composition is only 104.0, or almost 1.5 numbers below that achieved by use of the T.E.L. alone. This demonstrates that hexaethylbenzene molybdenum tricarbonyl is actually detrimental to the knock-suppressing effectiveness of the organo-lead compound. In contradistinction, hexamethylbenzene molybdenum tricarbonyl, a closely-related material, provides a synergistic octane improvement when used with T.E.L., as demonstrated in Example I. Motor fuels containing hexaethylbenzene molybdenum tricarbonyl in addition to an organo-lead anti-knock compound, are not within the scope of this invention.

Example III Undesirable results are also obtained in similar experimental work with tetraisopropylbenzene molybdenum tricarbonyl. Thus, when 0.805 weight percent of this complex is added to a base fuel consisting predominately of saturated hydrocarbons boiling in the gasoline range, the R.O.N. of the base fuel remains unchanged at 87.3. Incorporation of 3 cc. of T.E.L. per gallon in the base fuel raises the R.O.N. to 100.0, whereas the addition of both T.E.L. and tetraisopropylbenzene molybdenum tricarbonyl in the same respective concentrations, results in elevating the R.O.N. to only 98.3. Tetraisopropylbenzene molybdenum tricarbonyl is thus also detrimental to T.E.L. and, consequently, is not contemplated as within the scope of the invention.

Example IV The behavior of 1,3,5-trimethylbenzene molybdenum tricarbonyl is similar to that of hexaethylbenzene molybdenum tricarbonyl and tetraisopropylbenzene molybdenum tricarbonyl as described in Examples II and III above. Thus, 0.40 weight percent of 1,3,5-trimethylbenzene molybdenum tricarbonyl in a conventional catalytic gasoline, having an approximate volumetric composition of 35 percent saturated hydrocarbons and 65 percent aromatic and olefinic hydrocarbons, causes no change in the base fuels R.O.N. of 88.9. Addition of 3 cc. of T.E.L. per gallon to the base fuel does raise the R.O.N. significantly, viz., to 96.7, as would he expected. However, when both 1,3,5-trimethylbenzene molybdenum tricarbonyl and T.E.L. are present together in the base fuel, in the same respective concentrations, the R.O.N. is raised to only 92.9, or lower by almost 4 Research octane numbers than when T.E.L. is employed alone.

In view of the above results, it is apparent that the synergistic octane quality improvement provided by employing hexamethylbenzene molybdenum tricarbonyl with T.E.L. in motor fuels is unexpected, and indeed surprising, in view of the adverse behavior of other closely-related complexes not within the scope of the invention. When other aromatic-molybdenum 'tricarbonyl complexes which are within the scope of the invention are employed together with T.E.L., or with other organolead anti-knock compounds, benefits similar to those achieved with hexamethylbenzene molybdenum tricarbonyl are obtained.

In my copending patent application of even filing date, Serial No. 780,244, I have disclosed and claimed hexa- 6 methylbenzene molybdenum tricarbonyl as a new composition of matter.

The invention claimed is:

1. A spark ignition internal combustion engine fuel composition consisting essentially of petroleum hydrocarbons boiling within the gasoline range, an antiknock amount of a tetra-alkyl lead antiknock compound, and a small amount, sufficient to provide a synergistic octane quality improvement in combination with said organo lead compound, of hexamethylbenzene molybdenum tricarbonyl.

2. A full composition according to claim 1 wherein said tetra-alkyl lead compound is tetraetyl lead.

References Cited in the file of this patent UNITED STATES PATENTS 1,579,802 Babb Apr. 6, 1926 1,779,061 Danner et al. Oct. 21, 1930 1,954,865 Danner Apr. 17, 1934 2,086,775 Lyons et a1. July 13, 1937 2,314,575 Doran Mar. 23, 1943 2,356,476 Shappin'o Aug. 22, 1944 2,737,932 Thomas Mar. 13, 1956 2,881,062 Bishop Apr. 7, 1959 FOREIGN PATENTS 779,814 Great Britain July 24, 1957 1,080,357 France May 26, 1954 1,095,084 France Dec. 15, 1954 OTHER REFERENCES Proceedings of the Chemical Society (London), May 1958, page 152, A General Method for Preparing Tricarbonylchromium Derivatives of Aromatic Compoun by Nicholls et a1. 

1. A SPARK IGNITION INTERNAL COMBUSTION ENGINE FUEL COMPOSITION CONSISTING ESSENTIALLY OF PETROLEUM HYDROCARBONS BOILING WITHIN THE GASOLINE RANGE, AN ANTIKNOCK AMOUNT OF A TETRA-ALKYL LEAD ANTIKNOCK COMPOUND, AND A SMALL AMOUNT, SUFFICIENT TO PROVIDE A SYNERGISTIC OCTANE QUALITY IMPROVEMENT IN COMBINATION WITH SAID ORGANOLEAD COMPOUND, OF HEXAMETHYLBENZENE MOLYBDENUM TRICARBONYL. 